﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp4
{
    class Program
    {
        static void Main(string[] args)
        {
            string userName = "小米";//驼峰命名   
            string UserName = "大米";//帕斯卡命名
            const double PI = 3.1415926;
            const float P = 3.14f;
            double r = 4;
            double area = r * r * PI;
            Console.WriteLine(area);//常量
            var res = 2 > 1;
            int num = 10;
            if (res)
            {
                Console.WriteLine("看到这个说明你对了"); 
            }//最简单的判断句
            if (res)
            {
                Console.WriteLine("看到这个说明你对了");
            }
            else
            {
                Console.WriteLine("看到这个说明你错了");
            }//双分支
            if (num > 5)
            {
                Console.WriteLine("大于5");
            }
            else if (num > 4)
            {
                Console.WriteLine("大于4");
            }
            else if (num > 3)
            {
                Console.WriteLine("大于3");
            }
            else {
                Console.WriteLine("小于等于2 ");
            }
            Console.WriteLine("请输入学生的成绩（0~100的整数）");
            int points = int.Parse(Console.ReadLine());
            switch (points / 10)
            {
                case 10:
                case 9:
                    Console.WriteLine("优秀");
                    break;
                case 8:
                case7: Console.WriteLine("良好");
                    break;
                case 6:Console.WriteLine("及格");
                    break;
                default:Console.WriteLine("不及格");
                    break;


            }//switch  case法

            
        }
    }
}
